子集

 
#include<stdio.h>
int s[10] = {0};


void subset(int i, int n, int r)
{
    int b[10] = {0};
    int j, k = 0;
    if(i == n)
    {
            for(j = n-1, k = 0; j >= 0; j --)
            {
                        if(s[j] == 0)
                            continue;
                        else
                            {
                                 b[k++] = j+1;
                            }                
                    }
            if( k == r)
            {
                        for(i = 0; i < k; i ++)
                            printf("%d",b[i]);
                        printf("\n");
                    }
            
            return ;

        }
    else
    {
            s[i] = 0;//
            subset(i+1, n, r);
            s[i] = 1;
            subset(i+1, n, r);
        }
}


int main()
{
    int n,r;
    scanf("%d%d", &n, &r);
    getchar();
    subset(0, n, r);
    return 0;
}        
每个数的0，1 表示出没出现过